1. ∞
(a)Starting with the geometric series Σ x^n , find the sum of the series
n=0
∞
Σ nx^(n-1) , |x| < 1
n=1
∞
(b)Find the sum of the series Σ n/2^n
n=1
2.Find the radious of convergence and interval of convergence of the series
∞ (-3)^n．x^n
Σ --------------
n=0 √(n+1)
這兩題...麻煩各位大大了@@
級數是我沒學過的，都靠自己看，所以感覺很不扎實
希望大大們能多多指教^^
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